23.3 Interventional Pain Procedures & Anesthesia for Pain Management Cases
Key Takeaways
- Cervical transforaminal epidural injections require non-particulate dexamethasone, because particulate steroids can embolize through a radicular artery and cause spinal cord or brainstem infarction.
- Stellate ganglion block is never performed bilaterally, and injection of under 1 mL into the vertebral artery causes immediate seizure; successful block produces Horner syndrome.
- Celiac plexus block reliably produces orthostatic hypotension and diarrhea from splanchnic sympathectomy, so intravenous preloading is required.
- Abrupt intrathecal baclofen withdrawal causes fever, rigidity, and rhabdomyolysis that mimics malignant hyperthermia, and the treatment is restoration of baclofen plus benzodiazepines, not dantrolene.
- Sedation for interventional pain procedures must remain light enough for the patient to report paresthesia and radicular pain, which is the only early warning of intraneural or intrathecal injection.
Why This Topic Matters on the NCE
Domain IV.A.7.c of the content outline lists pain management procedures as a distinct surgical and diagnostic category the CRNA is expected to support, and Domain III.L covers the management they deliver. These cases look easy — brief, prone, "just a little sedation" — and they contain some of the highest-consequence complications in the outline, including permanent spinal cord infarction and seizure from a fraction of a milliliter of local anesthetic.
1. The Governing Constraint: Sedation Must Preserve Feedback
Most interventional pain procedures require the patient to be responsive enough to report paresthesia, radicular pain on injection, and new neurologic symptoms. Deep sedation removes the only early warning system that exists for intraneural or intrathecal injection.
- Target minimal to moderate sedation: low-dose midazolam and fentanyl, or a low-dose remifentanil or dexmedetomidine infusion.
- Avoid dense sedation or general anesthesia except for children, patients who cannot cooperate, and specific procedures such as intrathecal pump or spinal cord stimulator implantation.
- Prone positioning with the head turned, arms abducted, and limited airway access is standard. Pressure points, the eyes, the brachial plexus, and the ulnar nerve all require deliberate attention, and an airway plan for the prone patient must exist before sedation begins.
- Fluoroscopy means radiation exposure for the team on every case.
2. Neuraxial and Spinal Procedures
Epidural steroid injection
Delivered by interlaminar, transforaminal, or caudal approach for radicular pain.
The single highest-yield safety rule in interventional pain medicine: for cervical transforaminal injections, only non-particulate steroid (dexamethasone) may be used. Particulate preparations — methylprednisolone, triamcinolone, betamethasone — form aggregates that can embolize through a radicular artery and cause spinal cord or brainstem infarction. The same concern applies to lumbar transforaminal injections near the artery of Adamkiewicz, typically arising between T9 and L2 on the left.
Other complications: dural puncture and postdural puncture headache, epidural hematoma, epidural abscess, transient systemic steroid effects including hyperglycemia and adrenal suppression, and vasovagal reaction.
Facet joint interventions
Medial branch blocks diagnose facet-mediated pain; if two diagnostic blocks are positive, radiofrequency ablation of the medial branches provides longer relief. Local anesthetic volume must be small and precise, because larger volumes spread to the epidural space and invalidate the diagnostic result.
Vertebroplasty and kyphoplasty
Polymethylmethacrylate cement injected into a compression-fractured vertebral body. The hazard is cement extravasation and embolism — into the epidural venous plexus causing cord compression, or into the pulmonary circulation causing hypoxemia and cardiovascular collapse, the same physiology as bone cement implantation syndrome.
Spinal cord stimulator and intrathecal pump implantation
Implantation is usually done under general anesthesia or deep sedation with a period of intraoperative awake testing for lead placement in some systems.
Intrathecal baclofen withdrawal is a life-threatening emergency that every CRNA should recognize: abrupt interruption of pump delivery — from battery depletion, catheter kink, or programming error — produces high fever, severe rigidity, altered mental status, and rhabdomyolysis. It closely mimics neuroleptic malignant syndrome and malignant hyperthermia. Treatment is restoration of baclofen (intrathecal if possible, high-dose oral otherwise) plus benzodiazepines and supportive care; dantrolene is not the definitive therapy. Intrathecal drug delivery may also contain morphine, hydromorphone, clonidine, bupivacaine, or ziconotide.
3. Sympathetic Blocks
| Block | Landmark / level | Indication | Signature complication |
|---|---|---|---|
| Stellate ganglion | C6 transverse process (Chassaignac tubercle) | Upper limb CRPS, vascular insufficiency | Never perform bilaterally; recurrent laryngeal nerve block causes hoarseness, phrenic block causes hemidiaphragm paralysis; vertebral artery injection causes seizure with under 1 mL |
| Celiac plexus | Anterolateral to the aorta at T12 to L1 | Pancreatic and upper abdominal cancer pain | Orthostatic hypotension and diarrhea from sympathectomy; paraplegia from artery of Adamkiewicz injury; retroperitoneal hematoma; pneumothorax |
| Lumbar sympathetic | Anterolateral L2 to L4 vertebral bodies | Lower limb CRPS, ischemic pain | Genitofemoral neuralgia, ureteral injury, hypotension |
| Superior hypogastric plexus | Anterior to L5 to S1 | Pelvic visceral cancer pain | Vascular puncture, bowel or bladder injury |
| Ganglion impar | Anterior to the sacrococcygeal junction | Perineal and coccygeal pain | Rectal perforation, infection |
A successful stellate ganglion block produces Horner syndrome — ptosis, miosis, and anhidrosis on the blocked side — which confirms sympathetic blockade of the head, though it does not by itself confirm adequate upper limb sympathectomy. Additional signs are conjunctival injection, nasal congestion, and a rise in ipsilateral hand temperature.
Because celiac plexus blockade removes splanchnic sympathetic tone from a large vascular bed, preload with intravenous fluid and anticipate significant hypotension.
4. Anticoagulation and Bleeding Risk
ASRA publishes a separate guideline for interventional spine and pain procedures distinct from its regional anesthesia guideline. Procedures are stratified by bleeding risk:
- High risk: spinal cord stimulator and intrathecal pump implantation, vertebroplasty and kyphoplasty, epidural procedures in the cervical and thoracic spine
- Intermediate risk: interlaminar and transforaminal epidural injections, sympathetic blocks, facet radiofrequency
- Low risk: trigger point injections, peripheral joint injections, sacroiliac injections
Anticoagulant and antiplatelet hold intervals follow the risk tier, and for high-risk neuraxial procedures they mirror the neuraxial anesthesia intervals. Assume the interventional pain guideline is stricter than you expect, and verify the specific hold interval for the specific drug.
5. Contrast, Infection, and Monitoring
- Iodinated contrast is injected under live fluoroscopy to confirm needle position and to exclude intravascular or intrathecal spread. Prior anaphylactoid reaction requires corticosteroid and antihistamine premedication; gadolinium is an alternative in some circumstances.
- Strict aseptic technique is mandatory — epidural abscess and meningitis are catastrophic and are reportable adverse events.
- Standard ASA monitoring applies in every location, including the pain clinic, and capnography is required whenever moderate or deep sedation is delivered.
Exam Traps
- Cervical transforaminal injections require non-particulate steroid (dexamethasone). Particulate steroid can cause cord infarction.
- A stellate ganglion block is never done bilaterally — bilateral recurrent laryngeal nerve block obstructs the airway.
- Fever plus rigidity in a patient with an intrathecal pump is baclofen withdrawal, not malignant hyperthermia.
- Celiac plexus block causes hypotension and diarrhea. Preload the patient.
- Do not sedate deeply — the patient's report of paresthesia is the safety monitor.
A patient is scheduled for a right C6 transforaminal epidural steroid injection for cervical radiculopathy. Which steroid preparation must be used and why?
Immediately after injection of 0.5 mL of local anesthetic during a right stellate ganglion block, the patient has a generalized tonic-clonic seizure. What is the most likely cause?
A patient with an implanted intrathecal baclofen pump presents to the emergency department with a temperature of 40.1 C, severe generalized rigidity, altered mental status, and a creatine kinase of 8,000 units/L. What is the definitive treatment?
Why should sedation for a diagnostic transforaminal epidural injection be kept at a minimal to moderate level?